DIASTROPHISM AND THE FORMATIVE PROCESSES 685 



SO fast a rate of infall as this does not seem to be warranted by 

 the mechanics of the case. 



Apparently the only line of escape from the import of such a 

 serial trial lies in postulating that the rate of infall in the earliest 

 stages was sufficiently more rapid than the mean rate to effect 

 melting in such early period. A declining rate of infall is, of course, 

 to be presumed, and has been taken into account. The rate used 

 in the computations is the mean rate for the specified accession 

 when assumed to be distributed over only the period vfhich. followed 

 the formation of the earth-core and preceded the earliest time- 

 determined Archean, 16X10* years ago. The accessions before 

 that period were reckoned as part of the mass of the earth-core, 

 and the accessions since were thrown into the specified period to 

 avoid counting the long tailing-out period of 1,600,000,000 years 

 (radioactive scale). The period thus made the basis of compu- 

 tation represents an intermediate stage of infall and was given the 

 benefit constructively of all subsequent infall. We excluded such 

 infall as was contemporaneous with the evolution of the nucleus 

 from its nebulous state until a definite earth-core was formed, 

 because it necessarily preceded life-evolution, and because it is 

 not separable from nebulous condensation and the other nuclear 

 conditions. In connection with the irregularities of the original 

 outburst, there may have arisen some incalculable rates of infall. 

 These would doubtless have made themselves felt chiefly in the 

 nuclear stages. Our endeavor was to include in the computations 

 only the systematic ingathering into which the action settled as a 

 secular process. The physical state of the nucleus during its 

 evolution from a nebulous state into an earth-core has been left 

 an open question, reserved for further consideration. Meanwhile, 

 a molten state during that period has been treated as one of the 

 alternatives, and as a not improbable one. The infall of planet- 

 esimals during that stage may probably have been an unportant 

 factor in determining the state which actually prevailed. But all 

 that is held to antedate the growth of the outer part of the earth. 

 This embraces about all that has yet been brought under study in 

 geological and biological inquiries. To reach a satisfactory basis 

 for these inquiries is the soul of the present issue. The state of 



